This kit is The One for a direct OEM parts upgrade; fits without modifications. Designed to pinpoint & eliminate weak points in the OEM M8 rocker design. Especially advised when changing to a hot cam (+.550" lift) and more performance in general. This kit combines several S&S sets to provide you with one complete top-end set up that includes everything for the engine to remain dependable with high horsepower and torque numbers. This Top End Gardian kit includes S&S 917702 +66% stronger rocker arm shafts; that replace OEM 17300059B. S&S 587241 rocker arm stud & nut kit; that replaces the OEM 10200503 bolts to prevent rockers coming loose and excessive wear on the tower studs. S&S 576972 cold rolled 8640 heat treated head bolt set; with 200.000 psi tensile strength; replaces OEM 10200303 head bolts and S&S 597871 roller rocker arms which prevent excessive valve thrust and stress; as happens with higher lift cams running at high RPM.